Identification Of Bacteria Question And Answers

Identification Of Bacteria Important Notes

1. Types of microscopy used for the identification of bacteria

  • Optical or light microscopy
  • Phase contrast microscopy
  • Darkfield microscopy
  • Interference microscope
  • Polarization microscope
  • Electronic microscope

2. Staining of bacteria

Identification Of Bacteria Staining of bacteria

Identification Of Bacteria Short Answers

Question 1. Indole test?

Indole test Principle: To determine the ability of an organism to decompose amino acid tryptophan into indole.

Indole test Procedure:

  • Inoculate the test bacterium into tryptophan-rich peptone water and incubate at 37°C for 48-96 hours.
  • 0.5 ml of Kovac’s reagent is added and gently shaken.

Indole test Interpretation:

  • Indole positive – A red-coloured ring near the surface of the medium
  • Indole negative – A yellow-coloured ring near the surface of the medium.

Indole test Use:

  • To identify and classify bacteria.
    • Indole positive: E.Coli, Proteus species
    • Indole negative: Klebsiella species

Question 2. Urease test?

Urease test Principle: To determine the ability of an organism to produce an enzyme urease which splits urea to ammonia.

Urease test Procedure:

  • The test is done is Christensen’s urease medium
  • Test organism was inoculated on the entire slope of the medium and incubated at 37°C.
  • It is examined after 4 hours and overnight incubation.

Read And Learn More: Microbiology Question and Answers

Urease test Interpretation:

Identification Of Bacteria Urease test interpretation

Question 3. Voges – proskouev test:

Voges – Proskauer test Principle: This test depends on the production of acetyl methyl- carbinol from pyruvic acid as an intermediate stage in its conversion to 2:3 butylene glycol.

Voges – proskouev test Procedure:

  • 1 ml of glucose phosphate medium culture of the organisms incubated at 30°C for 5 days (or) 37°C for 48 hours is taken
  • Then 1 volume (0.2 ml) of 40% KOH and 3 volumes (0.6 ml) of 5% a-naphthol solution in ethanol are added.

Voges – proskouev test Interpretation:

  • Positive- Pink colour appears in 2 – Minutes
  • Negative- No colour change for 30 minutes it remains colourless.

Identification Of Bacteria Identification And Antimicrobial Susceptibility Testing Of Bacteria Directly From Positive Blood Culture

Identification Of Bacteria Viva Voce

  1. Casoni test is used to diagnose hydatid cyst
  2. DNA in bacteria is composed of two strands of complementary nucleotides wound together
  3. Weil Felix reaction is used for typhus fever
  4. Paul Bunnel test is used for infectious mononucleosis
  5. Montoux test is used for tuberculosis
  6. Naggler’s reaction is used for Clostridium

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